Synthesis and specific heat of CaPdH _3-δ with the perovskite structure

Single-phase samples of the hydrogen-deficient perovskite hydride CaPdH _3-δ with δ = 0.9 have successfully been synthesized. First, a homogeneous alloy of CaPd was prepared through the hydrogenation and subsequent dehydrogenation of an inhomogeneous alloy of CaPd obtained through the induction melting of Ca and Pd metals. Next, CaPdH _3-δ with δ - 0.9 was synthesized through the hydrogenation of the homogeneous CaPd alloy at room temperature. No superconductivity has been observed above 2K in the magnetic-susceptibility measurements. The specific-heat measurements have revealed that there exist optical phonons due to hydrogen vibrations with the Einstein temperature as high as about 1000 K.